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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.LegacyCompletionHandler"></a><a class="link" href="LegacyCompletionHandler.html" title="Legacy completion handler requirements">Legacy
      completion handler requirements</a>
</h3></div></div></div>
<p>
        A legacy completion handler must meet the requirements for a <a class="link" href="Handler.html" title="Handlers">handler</a>.
        A legacy completion handler must meet the requirements of <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>
        types (C++Std [copyconstructible]). A value <code class="computeroutput"><span class="identifier">h</span></code>
        of a completion handler class should work correctly in the expression <code class="computeroutput"><span class="identifier">h</span><span class="special">()</span></code>.
      </p>
<h5>
<a name="boost_asio.reference.LegacyCompletionHandler.h0"></a>
        <span class="phrase"><a name="boost_asio.reference.LegacyCompletionHandler.examples"></a></span><a class="link" href="LegacyCompletionHandler.html#boost_asio.reference.LegacyCompletionHandler.examples">Examples</a>
      </h5>
<p>
        A free function as a completion handler:
      </p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">completion_handler</span><span class="special">()</span>
<span class="special">{</span>
  <span class="special">...</span>
<span class="special">}</span>
</pre>
<p>
        A completion handler function object:
      </p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">completion_handler</span>
<span class="special">{</span>
  <span class="special">...</span>
  <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()()</span>
  <span class="special">{</span>
    <span class="special">...</span>
  <span class="special">}</span>
  <span class="special">...</span>
<span class="special">};</span>
</pre>
<p>
        A lambda as a completion handler:
      </p>
<pre class="programlisting"><span class="identifier">my_io_service</span><span class="special">.</span><span class="identifier">post</span><span class="special">(</span>
    <span class="special">[]()</span>
    <span class="special">{</span>
      <span class="special">...</span>
    <span class="special">});</span>
</pre>
<p>
        A non-static class member function adapted to a completion handler using
        <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">bind</span><span class="special">()</span></code>:
      </p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">my_class</span><span class="special">::</span><span class="identifier">completion_handler</span><span class="special">()</span>
<span class="special">{</span>
  <span class="special">...</span>
<span class="special">}</span>
<span class="special">...</span>
<span class="identifier">my_io_service</span><span class="special">.</span><span class="identifier">post</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(&amp;</span><span class="identifier">my_class</span><span class="special">::</span><span class="identifier">completion_handler</span><span class="special">,</span> <span class="keyword">this</span><span class="special">));</span>
</pre>
<p>
        A non-static class member function adapted to a completion handler using
        <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">()</span></code>:
      </p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">my_class</span><span class="special">::</span><span class="identifier">completion_handler</span><span class="special">()</span>
<span class="special">{</span>
  <span class="special">...</span>
<span class="special">}</span>
<span class="special">...</span>
<span class="identifier">my_io_service</span><span class="special">.</span><span class="identifier">post</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">bind</span><span class="special">(&amp;</span><span class="identifier">my_class</span><span class="special">::</span><span class="identifier">completion_handler</span><span class="special">,</span> <span class="keyword">this</span><span class="special">));</span>
</pre>
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<div class="copyright-footer">Copyright © 2003-2024 Christopher M. Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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